Distributed process control systems, like those used in chemical, petroleum or other process plants, typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses, or via a wireless communication link or network. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure, level and flow rate sensors), are located within the process environment and generally perform physical or process control functions such as opening or closing valves, measuring process parameters, etc. to control one or more process executing within the process plant or system. Smart field devices, such as the field devices conforming to the well-known Fieldbus, protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the controller. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices and execute a controller application that runs, for example, different control modules that make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices, such as HART®, WirelessHART®, and FOUNDATION® Fieldbus field devices. The control modules in the controller send the control signals over the communication lines or links to the field devices to thereby control the operation of at least a portion of the process plant or system.
Information from the field devices and the controller is usually made available over a data highway to one or more other hardware devices, such as operator workstations, personal computers or computing devices, data historians, report generators, centralized databases, or other centralized administrative computing devices that are typically placed in control rooms or other locations away from the harsher plant environment. Each of these hardware devices typically is centralized across the process plant or across a portion of the process plant. These hardware devices run applications that may, for example, enable an operator to perform functions with respect to controlling a process and/or operating the process plant, such as changing settings of the process control routine, modifying the operation of the control modules within the controllers or the field devices, viewing the current state of the process, viewing alarms generated by field devices and controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, keeping and updating a configuration database, etc. The data highway utilized by the hardware devices, controllers and field devices may include a wired communication path, a wireless communication path, or a combination of wired and wireless communication paths.
As an example, the DeltaV™ control system, sold by Emerson Process Management, includes multiple applications stored within and executed by different devices located at diverse places within a process plant. A configuration application, which resides in one or more operator workstations or computing devices, enables users to create or change process control modules and download these process control modules via a data highway to dedicated distributed controllers. Typically, these control modules are made up of communicatively interconnected function blocks, which are objects in an object oriented programming protocol that perform functions within the control scheme based on inputs thereto and that provide outputs to other function blocks within the control scheme. The configuration application may also allow a configuration designer to create or change operator interfaces which are used by a viewing application to display data to an operator and to enable the operator to change settings, such as set points, within the process control routines. Each dedicated controller and, in some cases, one or more field devices, stores and executes a respective controller application that runs the control modules assigned and downloaded thereto to implement actual process control functionality. The viewing applications, which may be executed on one or more operator workstations (or on one or more remote computing devices in communicative connection with the operator workstations and the data highway), receive data from the controller application via the data highway and display this data to process control system designers, operators, or users using the UIs, and may provide any of a number of different views, such as an operator's view, an engineer's view, a technician's view, etc. A data historian application is typically stored in and executed by a data historian device that collects and stores some or all of the data provided across the data highway while a configuration database application may run in a still further computer attached to the data highway to store the current process control routine configuration and data associated therewith. Alternatively, the configuration database may be located in the same workstation as the configuration application.
The architecture of process control plants and process control systems has been strongly influenced by limited controller and device memory, communications bandwidth, and controller and device processor capability. For example, the use of dynamic and static non-volatile memory in the controller is usually minimized or, at the least, carefully managed. As a result, during system configuration (e.g., a priori), a user typically must choose which data in the controller is to be archived or saved, the frequency at which it will be saved, and whether or not compression is used, and the controller is accordingly configured with this limited set of data rules. Consequently, data which could be useful in troubleshooting and process analysis is often not archived, and if it is collected, the useful information may have been lost due to data compression.
Additionally, to minimize controller memory usage in currently known process control systems, data that is to be archived or saved is reported to the workstation or computing device for storage, e.g., at the appropriate historian or data silo. The current techniques used to report the data utilize communication resources poorly and induce excessive controller loading. Additionally, due to the time delays in communication and sampling at the historian or silo, the data collection and time stamping are often out of sync with the actual process.
Similarly, in batch process control systems, to minimize controller memory usage, batch recipes and snapshots of controller configuration typically remain stored at a centralized administrative computing device or location (e.g., at a data silo or historian), and are transferred to a controller only when needed. Such a strategy introduces significant burst loads in the controller and in communication channels between the workstation or centralized administrative computing device and the controller.
Furthermore, the capability and performance limitations of relational databases of process control systems, combined with the high cost of disk storage, play a large part in structuring application data into independent entities or silos to meet the objectives of specific applications. For example, within the DeltaV™ system, process models, continuous historical data, and batch and event data are saved and/or archived in three different application databases or silos of data. Each silo has a different interface to access the data stored therein.
Structuring data in this manner creates a barrier in the way that historized data is accessed and used. For example, the root cause of variations in product quality may be associated with data in one or more of these data files. However, because of the different file structures it is not possible to provide tools that allow this data to be quickly and easily accessed for analysis. Further, audit or synchronizing functions must be performed to ensure that data across different silos is consistent.
The limitations of process plants and process control system discussed above, and other limitations, may undesirably manifest themselves in the operation and optimization of process plants or process control systems, for instance, during plant operations, trouble shooting, and/or predictive modeling. For example, such limitations force cumbersome and lengthy work flows that must be performed in order to obtain data for troubleshooting and generating updated models. Additionally, the obtained data may be inaccurate due to data compression, insufficient bandwidth, or shifted time stamps.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.